Structure for supporting a resonator using an ultrathin piezoelectric plate in a package

ABSTRACT

In a piezoelectric resonator having an ultrathin vibratory portion formed by a cavity made in a piezoelectric block and a thick frame-like rib formed integrally with said vibratory portion and surrounding it, an excess adhesive receiving groove or the like is cut in one marginal portion of the frame-like rib between an adhesive coated region. The resonator is fixedly housed in a package by use of an adhesive coated on one marginal portion of the frame-like rib along the z-axis direction, or by means of elastic pawls without using the adhesive. In this case, one marginal portion of the frame-like rib on the opposite side from a pad deposited on one side of the piezoelectric resonator is bonded to the bottom of the package. With such a structure, it is possible to prevent the adhesive from flowing into the cavity to cause variations in the resonance frequency of the piezoelectric resonator, to reduce the scatter of the temperature-frequency characteristic of a piezoelectric device using the resonator housed in a package during mass production, and to increase the bond strength of wire bonding for electrical connection of the piezoelectric resonator incorporated in the package.

TECHNICAL FIELD

The present invention relates to a structure by which a resonator usingan ultrathin piezoelectric plate capable of providing resonancefrequencies as high as tens to hundreds of megahertz can be supported ina package.

PRIOR ART

In recent years there has been a strong and growing demand for highfrequency operation and high frequency stability of various pieces ofelectronic and communication equipment. An ordinary AT cut quartzcrystal resonator, which has heretofore been used widely as apiezoelectric device (such as a resonator or filter), has a veryexcellent temperature-frequency characteristic; however, since itsresonance frequency is inversely proportional to its thickness, thefundamental frequency of this kind of resonator with a mechanicalstrength sufficient for practical use is around 40 MHz at the highest.

There has also been widely employed what is called overtone oscillationwhich extracts a higher order harmonic mode vibration of an AT cutquartz crystal resonator to obtain a frequency which is an odd multipleof the fundamental resonance frequency, but its oscillation circuitcalls for an LC tuning circuit including a coil, and hence is notsuitable for fabrication as a semiconductor IC, besides the overtoneoscillation circuit may sometimes be difficult to activate because sucha resonator has a large capacitance ratio and consequently a highimpedance level.

On the other hand, a surface acoustic wave (SAW) resonator, whoseoscillation frequency is determined by the pitch of electrodes of aninterdigital transducer, has come to be able to output a maximum of 1GHz or so due to the progress in photolithography, but a piezoelectricsubstrate usable for the SAW resonator is remarkably inferior to the ATcut quartz crystal in terms of temperature-frequency characteristic.

To solve the above-mentioned problems, there has been proposed such apiezoelectric resonator as shown in FIGS. 10(a) and (b).

That is, a cavity or recess 5 is formed, by machining or etching, in oneside of a block 1 of AT cut quartz crystal substantially centrallythereof as depicted in FIGS. 10(a) and (b) and the thickness of avibratory portion 2 forming the bottom of the cavity 5 is selected about16 μm, for example, if a fundamental resonance frequency of 100 MHz isdesired.

On the side of the block where the cavity 5 is formed, the ultrathinvibratory portion 2 is edged with a thick frame-like marginal portion(or) rib 3 formed integrally therewith. The ultrathin vibratory portion2 can be retained in its required shape by the frame-like rib 3. In thisinstance, it is preferable that excitation electrodes for thepiezoelectric block be composed of an overall electrode 12 formed on theside of the block where the cavity 5 is provided and a partial electrode14 and an electrode lead pattern 14a on the opposite side of the cavity5, the electrode lead member 14a extending from the partial electrode 14to one end face of the block.

It is customary and technically advantageous to house such a resonatorof the above construction upside down--with the cavity 5 facingdownward--in a ceramic or similar package 11 which has a concave housingspace 10 centrally thereof and to mechanically bond and electricallyconnect the top 3a of one side of the frame-like marginal portion 3, bya conductive adhesive coated in line thereon, to a conductive film 16which is exposed on the bottom of the housing space 10, hermeticallypasses through the package and is connected to an external lead member17 projecting out of or exposed on the outside of the package, as shownin FIG. 11(a).

The piezoelectric device of such a construction has turned out to bedefective in that since the resonator is very small, it is hard tocontrol the amount of conductive adhesive used for bonding the top 3a ofone side of the frame-shaped rib 3 to the bottom of the package 11, andconsequently, the excess adhesive may sometimes flow into the cavity 5and hence increases the thickness of the vibratory portion 2, causing avariation in the resonance frequency.

In view of the above-noted defects of the conventional resonator usingan ultrathin piezoelectric plate, a first object of the presentinvention is to provide a piezoelectric resonator support structure withwhich it is possible to support, in a package, a piezoelectric resonatorof the type having an ultrathin vibratory portion formed by the bottomof a cavity made in a block of quartz crystal or the like, withoutcausing a variation in the resonance frequency of the resonator which isattributable to the inflow of the excess adhesive into the cavity whichis likely to occur when fixing the top of one marginal portion of theframe-shaped rib of the resonator to the bottom of the package.

Incidentally, the inventors of the present invention have proposed inJapanese Patent Public Disclosure Gazette No. 52529/89 an electrodearrangement for the piezoelectric resonator using such an ultrathinpiezoelectric plate, which is composed of an overall electrode formed onthe side of the plate where the above-mentioned cavity is made and apartial electrode and an electrode lead pattern extending therefrom onthe planar surface of the piezoelectric block on the side opposite fromthe overall electrode. In the prior application it is also suggestedthat such an electrode arrangement does not call for any particularmethod or process therefor and allows ease in fixing mounting of theresonator in a flat package and in the connection of the one electrodeto an external lead member could easily be done, by fixing the resonatorat the side of the overall electrode to a conductive film which isexposed on the bottom of the package by use of a conductive adhesive.

However, substantially no studies have been made so far as to whatmethod should be used to fixedly mount the resonator of such structurein a required package without impairing its various characteristics,partly because the resonator has been confined to studies inlaboratories and has not been mass-produced. As a result of trialproduction of such a resonator as mentioned above, it has been found outthat it is difficult to define the area for bonding one marginal portionof the resonator to the bottom of the flat package by use of aconductive adhesive, because the resonator is primarily as small as 3 mm×3 mm so as to meet severe requirements for microminiaturization ofvarious pieces of electronic equipment. Furthermore, it has also beenfound out that strain or stress induced in the adhesive by its hardeningis applied directly to the resonator, inevitably causing variations inits resonance frequency and temperature-frequency characteristic afterpackaging.

In view of the fact that various characteristics of a piezoelectricresonator using such an ultrathin piezoelectric substrate as mentionedabove are appreciably influenced by the position where the resonator isfixed to a predetermined package, a second object of the presentinvention is to provide an ultrathin quartz crystal resonator supportstructure which suppresses scattering of various characteristics of thepiezoelectric device, in particular its temperature-frequencycharacteristic.

In the case of connecting bonding pads 14b formed on the planar surfaceof the resonator to external lead connecting pads 27, exposed in thepackage 11, by bonding wires 28 after fixedly mounting the resonator inthe package in such a manner as referred to above in respect of FIG. 11(a), the marginal portion 3 of the piezoelectric plate 1 where thebonding wires 28 are to be attached is pressed down and thepiezoelectric plate 1 is elastically bonded by a bonder around theadhering axis between the resonator and the bottom of the package andconsequently the pressure applied to the pad 14b is diminished, becausethe above-mentioned marginal portion of the piezoelectric plate isslightly spaced apart from the bottom of the package as seen from FIG.11(a). In consequence, the connection between the electrode lead patternand the bonding wire(s) may sometimes by insufficient, often causingtrouble such as disconnection of the latter from the former in amass-production test, impact and vibration tests, etc.

In view of the above-noted problems which are expected to encounter inthe fabrication of the resonator due to the structure of its electrodelead pattern connecting portions, a third object of the presentinvention is to provide an electrode lead structure which provides forincreased strength in wire bonding for electrical connection of theresonator incorporated in a package.

Apart from the foregoing, there are cases where the piezoelectricresonator is required to have an extremely severe temperature-frequencycharacteristic, but it is expected that such a severe requirement cannotbe met even by a combination of the above-described techniques.

It is therefore a fourth object of the present invention to provideresonator packaging structure which allows fixing the resonator to itspackage without using adhesive and permits electrical connection of theelectrodes formed on both sides of the piezoelectric plate to externallead members posed by the packaging of the resonator.

SUMMARY OF THE INVENTION

To attain the first object, the resonator using the ultrathinpiezoelectric plate of the present invention has an excess adhesivereceiving groove cut in the top of the marginal portion of theframe-like rib of the piezoelectric block along the portion to be coatedthe conductive adhesive at the side of the cavity.

To attain the second object, according to the present invention, the ATcut quartz crystal block forming the resonator is fixed to apredetermined package at positions along the z axis of one marginal edgeof the frame-like rib.

To attain the third object, according to the present invention, onemarginal portion of the frame-like rib which is opposite to a bondingpad formed at the same marginal portion of the piezoelectric block iscemented to the bottom of the package.

To attain the fourth object, according to the present invention, theresonator is fixed to the package by elastic claws projecting out fromthe inner wall or bottom of the package and the electrode of theresonator facing toward the bottom of the package is connected to aconductive pad on the other surface of the piezoelectric block via aconductive film deposited on the interior surface of a through holepiercing the piezoelectric block or a groove having a conductive coatingon the side of the block, for connection to an external lead member ofthe package.

BRIEF DESCRIPTION OF THE DRAWINGS

FIG. 1(a), (b) and (c) are a perspective view, a plan view and asectional view showing the construction of a quartz crystal resonatoraccording to a first embodiment of the present invention;

FIGS. 2(a) and (b) are plan views of modified forms of the FIG. 1embodiment;

FIG. 2(c) is a partial plan view of another modification;

FIGS. 3(a) and (b) are plan views of showing different examples ofresonators to which a second embodiment of the present invention is tobe applied;

FIGS 4(a) and (b) are graphs showing data of comparison tests forconfirming the effect by the second embodiment of the present invention;

FIG. 5(a) is a plan view illustrating a basic example of the ultrathinpiezoelectric resonator packaging structure according to a thirdembodiment of the present invention;

FIGS. 5(b), (c) and (d) are sectional views taken on the lines 5B--5B,5C--5C and 5D--5D in FIG. 5(a);

FIG. 6(a) is a partial sectional view illustrating a modified form ofthe third embodiment of the present invention;

FIG. 6(b) is a development showing claws for urging the resonator;

FIGS. 7(a) and (b) are a plan view and a sectional view illustratinganother modified form of the third embodiment of the present invention;

FIGS. 8(a) to (c) are a perspective view and a partial sectional viewsshowing still other modifications of the third embodiment of the presentinvention;

FIG. 9 is a longitudinal-sectional view explanatory of a fourthembodiment of the present invention, showing by way of example, how theresonator utilizing an electrode lead connecting structure according tothe fourth embodiment is housed in a package;

FIGS. 10(a) and (b) are a perspective view showing the construction ofconventional resonator using an ultrathin piezoelectric plate and asectional view taken on the line 10B--10B in FIG. 10(a), showing how theresonator is housed in a package; and

FIGS. 11(a) and (b) is a sectional view and a plan view showing how theconventional resonator using an ultrathin piezoelectric plate is housedin the package.

DETAILED DESCRIPTION OF THE INVENTION

The present invention will hereinafter be described in detail withrespect to its preferred embodiments shown in the accompanying drawings.

FIGS. 1(a) and (b) are a perspective view and a plan view illustratingthe construction of the resonator using an ultrathin quartz crystalplate fabricated in accordance with a first embodiment of the presentinvention, and

FIG. 1(c) is a sectional view taken on the line 1C--1C in FIG. 1(b). Asis the case with the afore-mentioned prior art example, the AT cutquartz crystal resonator has the cavity 5 formed by etching or machiningin one side of the rectangular parallelpipedec block 1 or AT cut quartzcrystal substantially centrally thereof so that the bottom of the cavity5 forms the untratin vibratory portion 2 edged with the thick frame-likemarginal portion (rib) 3. In this embodiment, however, the AT cut quartzcrystal resonator has an excess adhesive receiving groove 40 cut in thetop of the marginal portion of the rib 3 along the conductive adhesivecoated portion (for fixing the quartz crystal) 3a near the cavity 5 sothat excess adhesive 15, which oozes from the adhesive coated portionwhen bonding the resonator to the package, flows into the groove 40, andhence is prevented from flowing into the cavity 5.

The groove 40 can be formend by etching simultaneously with theformation of the cavity 5, and accordingly, any particular manufacturingstep is not needed therefor.

It is necessary that the groove 40 be formed substantially in parallelto the conductive adhesive coated region 3a and that its width, length,depth and shape be set so that the overflowing excess adhesive 15 can beprevented from flowing into the cavity 5. From this point of view, thegroove 40 may also be a slit extending through the frame-like marginalportion of the rib 3.

The groove 40 need not always be limited specifically to such astraight-shaped one as shown but may also be provided at both ends withlarge adhesive reservoirs 41 as depicted in FIG. 2(a). Alternatively, itis possible to open the groove 40 to one end of the quartz crystal block1 near the adhesive coated region 3a to let the excess adhesive 15 rundown to the bottom of the package through the open ends 42. Thus, thearea of bonding the quartz crystal block 1 to the bottom of the packagecan be defined.

In the above embodiment the resonator is fixedly held in a cantileveredfashion at one marginal portion of the frame-like rib. Such a structureis effective in the reduction of scattering of the resonance frequencyof the resonator, improving its temperature-frequency charactristic andother characteristics. With the structure, however, the resonator isvery likely to be broken down by flapping due to a vibration or shockapplied thereto. To avoid this, the marginal portion 3b of theframe-like rib opposite the adhesive coated region 3a across the cavity5 may sometimes by joined at one corner 3b' to the bottom of the packageat the sacrifice of improvement in the above-mentioned variouscharacteristics of the resonator. Also, in such an instance, a groove 45may preferably be provided as shown in FIG. 2(c) so as to define thearea of joining the portion 3b' to the bottom of the package.

The gist of each of the FIGS. 1 and 2 embodiments according to the firstaspect of the present invention resides in the structure for preventingthe adhesive from flowing into the cavity by forming the excess adhesivereceiving groove in the top of one marginal portion of the frame-likerib between the adhesive coated region and the cavity as describedabove. Hence, any structures capable of producing the same effect asmentioned above fall inside the scope of the present invention.

Although in the above the piezoelectric resonator is housed with itscavity facing toward the bottom of the package, it is needless to saythat the present invention is also applicable to the case where theresonator is housed with its planar surface facing toward the bottom ofthe package.

The above embodiments have been described with respect to the case wherethe piezoelectric resonator is a AT cut quartz crystal resonator, butthis should be construed as being merely illustrative of the inventionand the invention is applicable as well to devices which utilizepiezoelectric materials other than the AT quartz crystal. Moreover,while the embodiments have been described to employ the rectangularblock of a piezoelectric material, this configuration is needed merelyfor providing enhanced mass productivity of the resonator by use of abatch system, and hence the present invention is not limitedspecifically thereto. Accordingly, the present invention can equally beapplied to resonators of circular, polygonal and other forms as viewedfrom above.

Thus, the embodiments shown in FIGS. 1(a) to (c) and 2(a) to (c)according to the first aspect of the present invention are intended tosolve the afore-mentioned first object of the invention and are capableof substantially completely preventing that when the resonator havingthe ultrathin vibratory portion is joined to the bottom of its package,the excess adhesive flows into the vibratory portion of the resonator,causing a variation in its resonance frequency. Furthermore, theseembodiments call for any high precision adhesive dispenser, and hencerequire any particular equipment, and they permit simultaneous formationof the excess adhesive receiving groove with the cavity. Accordingly,the structures of the above embodiments not only improve the yield rateof product but also decrease the manufacturing cost of the type ofpiezoelectric resonator.

Next, embodiments according to the second aspect of the presentinvention for attaining the afore-mentioned second object thereof willbe described, based on experimental data.

As referred to previously, the inventor of the subject application hasfound out, in the mass-production test of the AT cut quartz crystalresonator depicted in FIGS. 10(a) and (b), that itstemperature-frequency characteristic appreciably scatters according tothe position where the resonator incorporated therein is bonded to thebottom of its package.

For further studies of this problem, the present inventors produced tensamples in which the resonator 9 was joined to the bottom of the packageat one marginal portion of the frame-like rib 3 along the z axis of theAT cut quartz crystal block 1 and ten samples in which the resonator 3was joined to bottom of the package along the x axis of the block 1, asshown in FIG. 3(a), and the conducted experiments on the scatter oftheir temperature-frequency characteristic. FIGS. 4(a) and (b) show theresults of the experiments.

As is evident from the experimental results, the scatter of thetemperature-frequency characteristic of the resonator fixed to thepackage along the z axis of the AT cut quartz crystal block 1 is lessthan in the case of the resonator fixed to the package along the x axisof the AT cut quartz crystal block 1.

As regards other characteristics, no significant differences wereobserved between the two types of piezoelectric devices, though noreference is made to experimental data.

It is not clear so far what brought about such experimental results, butat any rate, it is clear that the resonator of the type using the AT cutquartz crystal plate should be fixed to the package along the z axis.

While in the above the present invention has been described inconnection with the case where the resonator using a rectangular quartzcrystal block is fixedly jointed to the package at one marginal portionof the frame-like rib surrounding the cavity, the invention need notalways be limited specifically thereto. For instance, if the quartzcrystal block 1 is disc-shaped as depicted in FIG. 3(b), the adhesive 15needs only to be coated on a marginal portion along its z axis. Even ifthe resonator is fixedly joined to the package at one marginal portionalong the z axis on the planar surface of the quartz crystal block 1 onthe opposite side from the cavity 2, the above-mentioned effect can beobtained. The present invention is also applicable to a resonator of thetype having the partial electrode on the side of the AT cut quartzcrystal block 1 where the cavity 5 is provided and the overall electrodeon the opposite side, and the piezoelectric device including the AT cutquartz crystal plate according to the present invention may be either ofa resonator and a filter element (including what is called multimodequartz crystal filter element having split electrodes).

Incidentally, it will be convenient for mounting the resonator in thepackage that the region where to coat the adhesive is clearly indicatedby marking it with paint at both sides thereof.

The embodiments according to the second aspect of the present inventionare as described above, and hence afford reduction of the scatter of thetemperature-frequency characteristic of the ultrathin piezoelectricresonator in the mass production thereof, without involving anyparticular manufacturing step, thus ensuring the production ofpiezoelectric devices of uniform quality.

Next, an embodiment according to the third aspect of the presentinvention for attaining the afore-mentioned third object thereof will bedescribed with respect to a resonator using an ultrathin piezoelectricplate is housed in a package according to the third aspect of thepresent invention. The resonator has a cavity 215 formed by machining oretching in one side of, for example, a rectangular parallelpipedic block200 of AT cut quartz crystal substantially thereof so that the bottom ofthe cavity 215 forms a vibratory portion 216 which is mechanicallysupported by thick frame-like rib 217 surrounding it.

The quartz crystal block 200 is deposited over the entire area of itssurface where the cavity 215 is provided, with a conductive film to forman overall electrode 218. On the planar surface of the block 200 on theopposite side from the overall electrode 218 there are formed a partialelectrode 206 and an electrode lead pattern 231 extending therefrom. Thelead pattern 231 has its end portion formed by a bonding pad 234 whichis connected by a wire 233 to an external lead member 232 of package 20.On a stepped portion of the package 20 inside thereof, opposite the pad234, there is disposed a conductor pad 235 which is connected to theexternal lead member 232.

One marginal portion of the frame-like rib 217 on the opposite side fromthe pad 234 is joined to the bottom of the package and then the pads 234and 235 are connected by the wire 233.

With the above structure wherein one side of one marginal portion of thepiezoelectric body 200 is bonded to the bottom of the package and thepad 234 deposited on the other side of the marginal portion 217 iswire-bonded to the pad 235 deposited on the stepped portion on the innerwall of the package 20 facing toward the above-mentioned marginalportion, the bond strength of the pad 234 bonded to the bottom of thepackage 20 is effectively increased when the pad 234 is pressed by abonder head.

The above structure according to the third aspect of the presentinvention fully utilizes the bonding pressure of the wire bonder for theelectrical connection between the piezoelectric plate and the package,and hence ensure the connection between the electrode lead member of theresonator and the external lead member of the package, thus providingfor remarkably improved reliability of the piezoelectric device.

Next embodiments according to the fourth aspect of the present inventionfor attaining the afore-mentioned fourth object thereof will hereinafterbe described in detail.

As referred to previously, in the resonator of such a structure asdepicted in FIGS. 10(a) and (b), the quartz crystal block is so smallthat when one marginal portion of the frame-like rib is fixedly attachedto the bottom of the package by use of a conductive adhesive, strainresulting from hardening of the adhesive is applied directly to thequartz crystal block, causing a variation in the resonance frequency ofthe resonator and the scatter of its temperature-frequencycharacteristic.

To solve this problem, the resonator according to the present inventionbasically employs such a packaging structure as shown in FIGS. 5(a) to(d).

This embodiment does not employ the conventional method of fixing apiezoelectric resonator having an ultrathin vibratory portion 100directly to the bottom of a package by use of a conductive adhesive, butinstead fixes the resonator by pressing it at four corners withfork-shaped elastic claws extending from the inner wall of the package.

That is to say, the package 108 with the claws 116, 116 . . . can easilybe obtained by punching a thin plate of an elastic material such asphosphor bronze into a pattern having the claws 116, 116 . . . extendingfrom a lead frame 117, as shown, by forming the pattern as required andthen by embedding the lead frame 117 in the inner wall of the ceramicpackage 108 during its sinter forming.

As will be seen from FIG. 5(a), by inserting the resonator 100 into thepackage 108 having the claws 116, 116 . . . while at the same timepressing down their tips with the marginal edge of the resonator 100,the claws 116, 116 . . . are restored to their initial positions bytheir elasticity and press the resonator 100 at its four corners as soonas the resonator 100 is pressed down into contact with the bottom of thepackage 108.

In the case where the resonator 100 is housed in the package 108 by sucha method as mentioned above, however, no stable electrical connectioncan be established between an overall electrode 105 on the side wherethe cavity 102 of the resonator 100 is formed and a conductive filmdeposited on the bottom of the package 108.

FIG. 5(b) illustrates a structure which solves the above-noted problem.As shown in FIG. 5(b), a through hole 118 is made in a frame-like rib104 of the resonator 100 at an appropriate position so that the overallelectrode 105 of the resonator 100 and a conductive pad 119 on theopposite side therefrom are connected through a conductive filmdeposited on the interior surface of the through hole 118. Theconductive pad 119 and another conductive pad 120 deposited on a steppedportion of the inner wall of the package 108 are connected by a bondingwire 121 and the pad 120 is connected to an external lead member 111 viathe conductive film 109 on the bottom of the package, for instance.

The above is the basic embodiment of the resonator packaging structureaccording to the present invention, but the invention is not limitedspecifically thereto but may also be modified as shown in FIGS. 6(a) and(b), in which the elastic pawls 116, 116 . . . project out upward fromthe bottom of the package.

In this instance, it is preferable that the claws 116, 116 . . . beformed integrally with the conductive film 109 on the bottom of thepackage, because the package of such a structure can be used housing afilter element as well as for housing a piezoelectric resonator.

Incidentally, it is needless to say that a ceramic package for housing afilter element must be sufficiently grounded, and hence calls for such alarge-area conductive film as mentioned above.

By the way, since the quartz crystal plate and the claws are bothmicrominiature, considerable difficulties are encountered in theformation of the claws and in the positioning of the resonator withrespect to the claws when it is inserted into the package. FIGS. 7(a)and (b) illustrate a modified form of the packaging structure of thepresent invention which is a solution to this problem.

That is, simple-structured claws 122, 122 . . . each having its tip bentat an acute angle, extend upward from the conductive film 109 depositedon the bottom of the package so that they press the resonator 100 at itsfour corners, and at least one of the claws presses the conductive pad119 which forms a land of the through hole 118 of the resonator, the tipof this claw 122 being bonded to the pad 119 by a conductive adhesive123.

Such a structure as mentioned above ensures the electrical connectionbetween the overall electrode 105 of the resonator and the external leadmember 111 of the package 108, allows ease in the formation of tips ofthe claws and in the positioning of the resonator and the claws fortheir engagement and assures fixing the resonator to the package inposition.

While in the above the overall electrode 105 and the conductive paddeposited on the opposite sides of the resonator are connected via thethrough hole, they may also be connected through utilization of a recess124 made in one end face of the resonator as shown in FIGS. 8(a) to (c).

As shown in FIG. 8(a), individual resonators having ultrathin vibratoryportions to which the present invention is applied are obtained bysevering along demarcation lines 125 a piezoelectric wafer having formedthereon a number of olectrode patterns in alignment; accordingly, therecess 124 of a desired shape and construction can be made in one endface of each resonator by making a through hole in the wafer across thedemarcation line 125 and depositing a conductive film on the inner wallof the through hole prior to cutting the wafer into individual elements.By connecting the overall electrode 105 and a conductive film 126 on theopposite sides of the resonator through the recess 124 and pressing thepad 125 by the claw 116 or 122 and fixing them together by use of theconductive adhesive 123, it is possible to ensure fixing of theresonator to the package and the electrical connection between theoverall electrode and the external lead member 111 of the package.

In the case where the piezoelectric element to be housed in the overallelectrode 105 of the resonator 100 may be connected to the external leadmember 111 of the package via the claw 122 as shown in FIG. 8(b) becausethe conductive film 109 on the bottom of the package is not alwaysrequired. FIG. 8(c) shows another modification for use in the case wherethe piezoelectric element is a dual mode filter element. Since theoverall electrode 105 serves as an earth electrode and must be groundedsufficiently in this case, the overall electrode 10 is connected via aclaw 116 to the earth terminal 111, and further, the conductive film 109on the bottom of the package connected to the terminal 111 is connectedto the overall electrode 105.

Thus, the resonator having a ultrathin piezoelectric plate is almostfree from stress which causes a variation in its resonance frequency oraffects its temperature-frequency characteristic, besides the electricalconnection between each electrode of the resonator and the correspondingexternal terminal can be established without fail.

The packaging structure according to the fourth aspect of the presentinvention has such a construction as described above, and henceminimizes variations in the resonance frequency of the resonator using aultrathin piezoelectric plate before and after its packaging and thescatter of its temperature-frequency characteristic after packaging,thus producing a remarkable effect in improving the yield rate ofproduct and its reliability. Moreover, these effects compensate forincreased manufacturing costs by a somewhat complicated packagestructure.

We claim:
 1. A structure for supporting a resonator having an ultrathinpiezoelectric plate in a package, said structure comprising:an ultrathinvibratory portion and a thick rectangular frame-like rib formedintegrally with and surrounding said vibratory portion, said vibratoryportion and said rib being formed by a cavity made in a substantiallycentral portion of one side of a quartz crystal block; and means forpreventing adhesive from flowing into said cavity from an adhesivecoated region of the frame-like rib, said means comprising an excessadhesive receiving groove cut in one marginal portion of said frame-likerib between the adhesive coated region and an inner marginal edge ofsaid cavity.
 2. A structure for supporting a resonator having anultrathin piezoelectric plate in a package, said structure comprising:aquartz crystal resonator having an ultrathin vibratory portion and athick frame-like rib formed integrally with and surrounding saidvibratory portion, said vibratory portion and said rib being formed by acavity made in a substantially central portion of one side of an AT cutquartz crystal block; an electrode lead extending from one marginalportion of the frame-like rib to the vibratory portion; and means forbonding the resonator to the package comprising an adhesive coated ononly a side of said one marginal portion opposite said electrode lead.3. A structure for supporting a resonator having an ultrathinpiezoelectric plate in a package, comprising:a resonator having anultrathin vibratory portion and a thick frame-like rib formed integrallywith and surrounding said vibratory portion, said resonator formed by acavity made in a substantially central portion of one side of apiezoelectric plate; and means for biasing said one side of saidresonator toward a bottom surface of the package, said means comprisinga plurality of elastic pawls extending from an inner surface of thepackage.
 4. A structure for supporting a resonator having an ultrathinpiezoelectric plate as claimed in claim 3, further comprising:anelectrode lead pattern formed on said one side of said resonator; aconductive pad formed on an opposite side of said resonator oppositesaid one side; and means for connecting said conductive pad to a leadterminal exposed on an outside surface of said package; wherein saidelectrode lead pattern is electrically connected to the conductive padvia a recess formed in the frame-like rib.
 5. A structure for supportinga resonator having an ultrathin piezoelectric plate as claimed in claim4, wherein one of said elastic pawls is formed of a conductive materialand is connected to the lead terminal exposed on the outside surface ofsaid package, wherein said conductive pad is pressed by said one elasticpawl, and wherein said conductive pad and said elastic pawl are bondedtogether by a conductive adhesive.
 6. A structure for supporting aresonator having an ultrathin piezoelectric plate in a package,comprising:a resonator having an ultrathin vibratory portion and a thickframe-like rib formed integrally with and surrounding said vibratoryportion, said resonator being formed by a cavity made in a substantiallycentral portion in one side of a piezoelectric block; a partialelectrode disposed within said cavity; and an electrode lead patternextending from said partial electrode to an electrode lead end padformed on a marginal portion of said frame-like rib; wherein saidmarginal portion of said frame-like rib is bonded on a side thereofopposite said electrode lead end pad to a bottom surface of saidpackage.